#include <iostream>

const double PI = 3.14;

class Circle
{

private:
public:
    int r;
    double caculateZC()
    {
        return 2 * PI * r;
    }
};

int main(int argc, char const *argv[])
{
    Circle c1;
    c1.r = 10;
    std::cout << "圆的周长为：" << c1.caculateZC() << std::endl;
    return 0;
}
